mirror of
https://github.com/postgres/postgres.git
synced 2025-10-31 10:30:33 +03:00
148 lines
6.1 KiB
Plaintext
148 lines
6.1 KiB
Plaintext
From owner-pgsql-hackers@hub.org Sat Dec 18 17:22:09 1999
|
|
Received: from hub.org (hub.org [216.126.84.1])
|
|
by candle.pha.pa.us (8.9.0/8.9.0) with ESMTP id SAA10300
|
|
for <pgman@candle.pha.pa.us>; Sat, 18 Dec 1999 18:21:57 -0500 (EST)
|
|
Received: from localhost (majordom@localhost)
|
|
by hub.org (8.9.3/8.9.3) with SMTP id SAA74681;
|
|
Sat, 18 Dec 1999 18:17:56 -0500 (EST)
|
|
(envelope-from owner-pgsql-hackers)
|
|
Received: by hub.org (bulk_mailer v1.5); Sat, 18 Dec 1999 18:17:33 -0500
|
|
Received: (from majordom@localhost)
|
|
by hub.org (8.9.3/8.9.3) id SAA74549
|
|
for pgsql-hackers-outgoing; Sat, 18 Dec 1999 18:16:38 -0500 (EST)
|
|
(envelope-from owner-pgsql-hackers@postgreSQL.org)
|
|
Received: from biology.nmsu.edu (biology.NMSU.Edu [128.123.5.72])
|
|
by hub.org (8.9.3/8.9.3) with ESMTP id SAA74401
|
|
for <pgsql-hackers@postgreSQL.org>; Sat, 18 Dec 1999 18:15:20 -0500 (EST)
|
|
(envelope-from brook@biology.nmsu.edu)
|
|
Received: (from brook@localhost)
|
|
by biology.nmsu.edu (8.8.8/8.8.8) id QAA03433;
|
|
Sat, 18 Dec 1999 16:14:50 -0700 (MST)
|
|
Date: Sat, 18 Dec 1999 16:14:50 -0700 (MST)
|
|
Message-Id: <199912182314.QAA03433@biology.nmsu.edu>
|
|
X-Authentication-Warning: biology.nmsu.edu: brook set sender to brook@biology.nmsu.edu using -f
|
|
From: Brook Milligan <brook@biology.nmsu.edu>
|
|
To: pgman@candle.pha.pa.us
|
|
CC: peter_e@gmx.net, pgsql-hackers@postgreSQL.org
|
|
In-reply-to: <199912182026.PAA05926@candle.pha.pa.us> (message from Bruce
|
|
Momjian on Sat, 18 Dec 1999 15:26:15 -0500 (EST))
|
|
Subject: Re: [HACKERS] Re: [PATCHES] Lock
|
|
References: <199912182026.PAA05926@candle.pha.pa.us>
|
|
Sender: owner-pgsql-hackers@postgreSQL.org
|
|
Status: OR
|
|
|
|
> > * Allow LOCK TABLE tab1, tab2, tab3 so all tables locked in unison
|
|
|
|
Let me add to this. One problem is that my description would sometimes
|
|
lock the tables in different orders, and that is a recipe for deadlock.
|
|
|
|
If you have to release earlier locks to wait on a later lock, once you
|
|
get the later lock, you must release it and then start from the
|
|
beginning, locking them in order again. If you don't, the system could
|
|
report a deadlock at random times, which would be very bad.
|
|
|
|
I'll add something, too. :) I think this derived from a suggestion I
|
|
made long ago. My idea was that when multiple tables need locking, a
|
|
deadlock can occur in the process of doing them one at a time. My
|
|
suggested solution was based on an analogy with the way ethernet
|
|
packets work.
|
|
|
|
- go through the list locking tables along the way.
|
|
|
|
- if a lock cannot be obtained within some time, release some (all?) locks,
|
|
and try again after some random time.
|
|
|
|
- keep trying (and releasing as needed) until some other timeout
|
|
passes, and then punt.
|
|
|
|
My thought was that if colliding locks are occuring, some sequence of
|
|
relinquishing locks (not necessarily all of them with each trial),
|
|
waiting, and reasserting them should work around the collisions.
|
|
Introducing random components to this might reduce the overall waiting
|
|
time, but I suppose a careful analysis of this needs to be done.
|
|
Perhaps just releasing all of the locks, waiting a random time, and
|
|
trying again is enough.
|
|
|
|
Somehow there has to be a mechanism for atomically asserting locks on
|
|
more than one table.
|
|
|
|
Cheers,
|
|
Brook
|
|
|
|
************
|
|
|
|
From owner-pgsql-patches@hub.org Sat Dec 18 22:51:06 1999
|
|
Received: from renoir.op.net (root@renoir.op.net [207.29.195.4])
|
|
by candle.pha.pa.us (8.9.0/8.9.0) with ESMTP id XAA18409
|
|
for <pgman@candle.pha.pa.us>; Sat, 18 Dec 1999 23:51:05 -0500 (EST)
|
|
Received: from hub.org (hub.org [216.126.84.1]) by renoir.op.net (o1/$Revision: 1.1 $) with ESMTP id XAA27570 for <pgman@candle.pha.pa.us>; Sat, 18 Dec 1999 23:49:19 -0500 (EST)
|
|
Received: from hub.org (hub.org [216.126.84.1])
|
|
by hub.org (8.9.3/8.9.3) with ESMTP id XAA52323;
|
|
Sat, 18 Dec 1999 23:45:32 -0500 (EST)
|
|
(envelope-from owner-pgsql-patches@hub.org)
|
|
Received: by hub.org (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32)); Sat, 18 Dec 1999 23:44:37 +0000 (EST)
|
|
Received: (from majordom@localhost)
|
|
by hub.org (8.9.3/8.9.3) id XAA52107
|
|
for pgsql-patches-outgoing; Sat, 18 Dec 1999 23:43:37 -0500 (EST)
|
|
(envelope-from owner-pgsql-patches@postgreSQL.org)
|
|
Received: from fw.wintelcom.net (bright@ns1.wintelcom.net [209.1.153.20])
|
|
by hub.org (8.9.3/8.9.3) with ESMTP id XAA52012
|
|
for <patches@postgreSQL.org>; Sat, 18 Dec 1999 23:42:44 -0500 (EST)
|
|
(envelope-from bright@wintelcom.net)
|
|
Received: from localhost (bright@localhost)
|
|
by fw.wintelcom.net (8.9.3/8.9.3) with ESMTP id VAA19594;
|
|
Sat, 18 Dec 1999 21:12:09 -0800 (PST)
|
|
Date: Sat, 18 Dec 1999 21:12:09 -0800 (PST)
|
|
From: Alfred Perlstein <bright@wintelcom.net>
|
|
To: Bruce Momjian <pgman@candle.pha.pa.us>
|
|
cc: Peter Eisentraut <peter_e@gmx.net>, patches@postgreSQL.org
|
|
Subject: Re: [PATCHES] Lock
|
|
In-Reply-To: <199912181828.NAA01486@candle.pha.pa.us>
|
|
Message-ID: <Pine.BSF.4.21.9912182107170.12109-100000@fw.wintelcom.net>
|
|
MIME-Version: 1.0
|
|
Content-Type: TEXT/PLAIN; charset=US-ASCII
|
|
Sender: owner-pgsql-patches@postgreSQL.org
|
|
Precedence: bulk
|
|
Status: OR
|
|
|
|
On Sat, 18 Dec 1999, Bruce Momjian wrote:
|
|
|
|
> [Charset ISO-8859-1 unsupported, filtering to ASCII...]
|
|
> > I was looking at this
|
|
> >
|
|
> > * Allow LOCK TABLE tab1, tab2, tab3 so all tables locked in unison
|
|
> >
|
|
> > but I'm not sure if my solution is really what was wanted, because it
|
|
> > doesn't actually guarantee an all-or-nothing lock, it just locks each
|
|
> > table in order. Thus it's more like a syntax simplification and reduces
|
|
> > overhead.
|
|
> >
|
|
>
|
|
> It took a few minutes, but I remember the use for this. If you are
|
|
> going to hang waiting to lock tab3, you don't want to lock tab1 and tab2
|
|
> while you are waiting for tab3 lock. The user wanted all tables to lock
|
|
> in one operation without holding locks while waiting to complete all
|
|
> locking.
|
|
>
|
|
> Can you do the locks, and if one fails, not hang, but unlock the
|
|
> previous tables, go lock/hang on the failure, and go back and lock the
|
|
> others? Seems it would have to be some kind of lock/fail/unlock/wait
|
|
> loop.
|
|
>
|
|
> Does this make sense? It did to me.
|
|
|
|
Guys, have a look at:
|
|
|
|
http://www.freebsd.org/~terry/iml.txt
|
|
http://jazz.external.hp.com/training/sqltables/c5s17.html
|
|
|
|
It's a way to do locking with deadlock detection, and without loosing
|
|
your place in line for locks, very nifty imo.
|
|
|
|
-Alfred
|
|
|
|
|
|
************
|
|
|
|
|